diff --git a/src/pse/mdec.cpp b/src/pse/mdec.cpp
index 6fd252ba0..6066ec93a 100644
--- a/src/pse/mdec.cpp
+++ b/src/pse/mdec.cpp
@@ -24,9 +24,14 @@ void MDEC::Reset()
 
 bool MDEC::DoState(StateWrapper& sw)
 {
-  sw.Do(&m_status_register.bits);
+  sw.Do(&m_status.bits);
   sw.Do(&m_data_in_fifo);
   sw.Do(&m_data_out_fifo);
+  sw.Do(&m_command);
+  sw.Do(&m_command_parameter_count);
+  sw.Do(&m_iq_uv);
+  sw.Do(&m_iq_y);
+  sw.Do(&m_scale_table);
 
   return !sw.HasError();
 }
@@ -40,8 +45,8 @@ u32 MDEC::ReadRegister(u32 offset)
 
     case 4:
     {
-      Log_DebugPrintf("MDEC status register -> 0x%08X", m_status_register.bits);
-      return m_status_register.bits;
+      Log_DebugPrintf("MDEC status register -> 0x%08X", m_status.bits);
+      return m_status.bits;
     }
 
     default:
@@ -70,8 +75,8 @@ void MDEC::WriteRegister(u32 offset, u32 value)
       if (cr.reset)
         SoftReset();
 
-      m_status_register.data_in_request = cr.enable_dma_in;
-      m_status_register.data_out_request = cr.enable_dma_out;
+      m_status.data_in_request = cr.enable_dma_in;
+      m_status.data_out_request = cr.enable_dma_out;
       m_dma->SetRequest(DMA::Channel::MDECin, cr.enable_dma_in);
       m_dma->SetRequest(DMA::Channel::MDECout, cr.enable_dma_out);
 
@@ -98,7 +103,7 @@ void MDEC::DMAWrite(u32 value)
 
 void MDEC::SoftReset()
 {
-  m_status_register = {};
+  m_status = {};
   m_data_in_fifo.Clear();
   m_data_out_fifo.Clear();
 
@@ -107,33 +112,423 @@ void MDEC::SoftReset()
 
 void MDEC::UpdateStatusRegister()
 {
-  m_status_register.data_out_fifo_empty = m_data_out_fifo.IsEmpty();
-  m_status_register.data_in_fifo_full = m_data_in_fifo.IsFull();
+  m_status.data_out_fifo_empty = m_data_out_fifo.IsEmpty();
+  m_status.data_in_fifo_full = m_data_in_fifo.IsFull();
+
+  m_status.command_busy = !m_data_in_fifo.IsEmpty();
+  if (!m_data_in_fifo.IsEmpty())
+  {
+    const CommandWord cw{m_data_in_fifo.Peek(0)};
+    m_status.parameter_words_remaining = Truncate16(m_command_parameter_count - m_data_in_fifo.GetSize());
+  }
+  else
+  {
+    m_status.parameter_words_remaining = 0;
+  }
+}
+
+u32 MDEC::ReadDataRegister()
+{
+  if (m_data_out_fifo.IsEmpty())
+  {
+    // Log_WarningPrintf("MDEC data out FIFO empty on read");
+    return UINT32_C(0xFFFFFFFF);
+  }
+
+  const u32 value = m_data_out_fifo.Pop();
+  UpdateStatusRegister();
+  return value;
 }
 
 void MDEC::WriteCommandRegister(u32 value)
 {
   Log_DebugPrintf("MDEC command/data register <- 0x%08X", value);
 
+  if (m_data_in_fifo.IsEmpty())
+  {
+    // first word
+    const CommandWord cw{value};
+    m_command = cw.command;
+    m_status.data_output_depth = cw.data_output_depth;
+    m_status.data_output_signed = cw.data_output_signed;
+    m_status.data_output_bit15 = cw.data_output_bit15;
+
+    switch (cw.command)
+    {
+      case Command::DecodeMacroblock:
+        m_command_parameter_count = ZeroExtend32(cw.parameter_word_count.GetValue());
+        break;
+
+      case Command::SetIqTab:
+        m_command_parameter_count = 16 + (((value & 1) != 0) ? 16 : 0);
+        break;
+
+      case Command::SetScale:
+        m_command_parameter_count = 32;
+        break;
+
+      default:
+        Panic("Unknown command");
+        break;
+    }
+
+    Log_DebugPrintf("MDEC command: 0x%08X (%u, %u words in parameter, %u expected)", cw.bits,
+                    ZeroExtend32(static_cast<u8>(cw.command.GetValue())),
+                    ZeroExtend32(cw.parameter_word_count.GetValue()), m_command_parameter_count);
+  }
+
   m_data_in_fifo.Push(value);
-  HandleCommand();
+
+  if (m_data_in_fifo.GetSize() <= m_command_parameter_count)
+  {
+    UpdateStatusRegister();
+    return;
+  }
+
+  // pop command
+  m_data_in_fifo.RemoveOne();
+  switch (m_command)
+  {
+    case Command::DecodeMacroblock:
+      HandleDecodeMacroblockCommand();
+      break;
+
+    case Command::SetIqTab:
+      HandleSetQuantTableCommand();
+      break;
+
+    case Command::SetScale:
+      HandleSetScaleCommand();
+      break;
+  }
+
+  m_data_in_fifo.Clear();
+  m_command = Command::None;
+  m_command_parameter_count = 0;
   UpdateStatusRegister();
 }
 
-u32 MDEC::ReadDataRegister()
+void MDEC::HandleDecodeMacroblockCommand()
 {
-  if (m_data_out_fifo.IsEmpty())
+  // TODO: Remove this copy and strict aliasing violation..
+  std::vector<u16> temp(m_data_in_fifo.GetSize() * 2);
+  m_data_in_fifo.PopRange(reinterpret_cast<u32*>(temp.data()), m_data_in_fifo.GetSize());
+
+  const u16* src = temp.data();
+  const u16* src_end = src + temp.size();
+
+  if (m_status.data_output_depth <= DataOutputDepth_8Bit)
   {
-    Log_WarningPrintf("MDEC data out FIFO empty on read");
-    return UINT32_C(0xFFFFFFFF);
+    while (src != src_end)
+    {
+      src = DecodeMonoMacroblock(src, src_end);
+      Log_InfoPrint("Decoded mono macroblock");
+    }
+  }
+  else
+  {
+    while (src != src_end)
+    {
+      src = DecodeColoredMacroblock(src, src_end);
+      Log_InfoPrint("Decoded colour macroblock");
+    }
   }
+}
 
-  const u32 value = m_data_out_fifo.Pop();
-  UpdateStatusRegister();
-  return value;
+const u16* MDEC::DecodeMonoMacroblock(const u16* src, const u16* src_end)
+{
+  std::array<s16, 64> Yblk;
+  if (!rl_decode_block(Yblk.data(), src, src_end, m_iq_y.data()))
+    return src_end;
+
+  std::array<u8, 64> out_r;
+  y_to_mono(Yblk, out_r);
+
+  switch (m_status.data_output_depth)
+  {
+    case DataOutputDepth_4Bit:
+    {
+      const u8* in_ptr = out_r.data();
+      for (u32 i = 0; i < (64 / 8); i++)
+      {
+        u32 value = ZeroExtend32(*(in_ptr++) >> 4);
+        value |= ZeroExtend32(*(in_ptr++) >> 4) << 4;
+        value |= ZeroExtend32(*(in_ptr++) >> 4) << 8;
+        value |= ZeroExtend32(*(in_ptr++) >> 4) << 12;
+        value |= ZeroExtend32(*(in_ptr++) >> 4) << 16;
+        value |= ZeroExtend32(*(in_ptr++) >> 4) << 20;
+        value |= ZeroExtend32(*(in_ptr++) >> 4) << 24;
+        value |= ZeroExtend32(*(in_ptr++) >> 4) << 28;
+        m_data_out_fifo.Push(value);
+      }
+    }
+    break;
+
+    case DataOutputDepth_8Bit:
+    {
+      const u8* in_ptr = out_r.data();
+      for (u32 i = 0; i < (64 / 4); i++)
+      {
+        u32 value = ZeroExtend32(*in_ptr++);
+        value |= ZeroExtend32(*in_ptr++) << 8;
+        value |= ZeroExtend32(*in_ptr++) << 16;
+        value |= ZeroExtend32(*in_ptr++) << 24;
+        m_data_out_fifo.Push(value);
+      }
+    }
+    break;
+
+    default:
+      break;
+  }
+
+  return src;
+}
+
+const u16* MDEC::DecodeColoredMacroblock(const u16* src, const u16* src_end)
+{
+  std::array<s16, 64> Crblk;
+  std::array<s16, 64> Cbblk;
+  std::array<std::array<s16, 64>, 4> Yblk;
+  std::array<u32, 256> out_rgb;
+
+  if (!rl_decode_block(Crblk.data(), src, src_end, m_iq_uv.data()) ||
+      !rl_decode_block(Cbblk.data(), src, src_end, m_iq_uv.data()) ||
+      !rl_decode_block(Yblk[0].data(), src, src_end, m_iq_y.data()) ||
+      !rl_decode_block(Yblk[1].data(), src, src_end, m_iq_y.data()) ||
+      !rl_decode_block(Yblk[2].data(), src, src_end, m_iq_y.data()) ||
+      !rl_decode_block(Yblk[3].data(), src, src_end, m_iq_y.data()))
+  {
+    return src_end;
+  }
+
+  yuv_to_rgb(0, 0, Crblk, Cbblk, Yblk[0], out_rgb);
+  yuv_to_rgb(0, 8, Crblk, Cbblk, Yblk[1], out_rgb);
+  yuv_to_rgb(8, 0, Crblk, Cbblk, Yblk[2], out_rgb);
+  yuv_to_rgb(8, 8, Crblk, Cbblk, Yblk[3], out_rgb);
+
+  switch (m_status.data_output_depth)
+  {
+    case DataOutputDepth_24Bit:
+    {
+      // pack tightly
+      u32 index = 0;
+      u32 state = 0;
+      u32 rgb = 0;
+      while (index < out_rgb.size())
+      {
+        switch (state)
+        {
+          case 0:
+            rgb = out_rgb[index++]; // RGB-
+            state = 1;
+            break;
+          case 1:
+            rgb |= (out_rgb[index] & 0xFF) << 24; // RGBR
+            m_data_out_fifo.Push(rgb);
+            rgb = out_rgb[index] >> 8; // GB--
+            index++;
+            state = 2;
+            break;
+          case 2:
+            rgb |= out_rgb[index] << 16; // GBRG
+            m_data_out_fifo.Push(rgb);
+            rgb = out_rgb[index] >> 16; // B---
+            index++;
+            state = 3;
+            break;
+          case 3:
+            rgb |= out_rgb[index] << 8; // BRGB
+            m_data_out_fifo.Push(rgb);
+            index++;
+            state = 0;
+            break;
+        }
+      }
+      break;
+    }
+
+    case DataOutputDepth_15Bit:
+    {
+      const u16 a = ZeroExtend16(m_status.data_output_bit15.GetValue());
+      for (u32 i = 0; i < static_cast<u32>(out_rgb.size());)
+      {
+        u32 color = out_rgb[i++];
+        u16 r = Truncate16((color >> 3) & 0x1Fu);
+        u16 g = Truncate16((color >> 11) & 0x1Fu);
+        u16 b = Truncate16((color >> 19) & 0x1Fu);
+        const u16 color15a = r | (g << 5) | (b << 10) | (a << 15);
+
+        color = out_rgb[i++];
+        r = Truncate16((color >> 3) & 0x1Fu);
+        g = Truncate16((color >> 11) & 0x1Fu);
+        b = Truncate16((color >> 19) & 0x1Fu);
+        const u16 color15b = r | (g << 5) | (b << 10) | (a << 15);
+
+        m_data_out_fifo.Push(ZeroExtend32(color15a) | (ZeroExtend32(color15b) << 16));
+      }
+    }
+    break;
+
+    default:
+      break;
+  }
+
+  return src;
+}
+
+static constexpr std::array<u8, 64> zigzag = {{0,  1,  5,  6,  14, 15, 27, 28, 2,  4,  7,  13, 16, 26, 29, 42,
+                                               3,  8,  12, 17, 25, 30, 41, 43, 9,  11, 18, 24, 31, 40, 44, 53,
+                                               10, 19, 23, 32, 39, 45, 52, 54, 20, 22, 33, 38, 46, 51, 55, 60,
+                                               21, 34, 37, 47, 50, 56, 59, 61, 35, 36, 48, 49, 57, 58, 62, 63}};
+
+bool MDEC::rl_decode_block(s16* blk, const u16*& src, const u16* src_end, const u8* qt)
+{
+  std::fill_n(blk, 64, s16(0));
+
+  // skip padding
+  u16 n;
+  for (;;)
+  {
+    if (src == src_end)
+      return false;
+
+    n = *(src++);
+    if (n == 0xFE00)
+      continue;
+    else
+      break;
+  }
+
+  u32 k = 0;
+  u16 q_scale = (n >> 10) & 0x3F;
+  s32 val = SignExtendN<10, s32>(static_cast<s32>(n & 0x3FF)) * static_cast<s32>(ZeroExtend32(qt[k]));
+
+  for (;;)
+  {
+    if (q_scale == 0)
+      val = SignExtendN<10, s32>(static_cast<s32>(n & 0x3FF)) * 2;
+
+    val = std::clamp(val, -0x400, 0x3FF);
+    // val = val * static_cast<s32>(ZeroExtend32(scalezag[i]));
+    if (q_scale > 0)
+      blk[zigzag[k]] = static_cast<s16>(val);
+    else if (q_scale == 0)
+      blk[k] = static_cast<s16>(val);
+
+    if (src == src_end)
+      break;
+
+    n = *(src++);
+    k += ((n >> 10) & 0x3F) + 1;
+    if (k >= 64)
+      break;
+
+    val = (SignExtendN<10, s32>(static_cast<s32>(n & 0x3FF)) * static_cast<s32>(ZeroExtend32(qt[k])) *
+             static_cast<s32>(q_scale) +
+           4) /
+          8;
+  }
+
+#undef READ_SRC
+
+  // insufficient coefficients
+  if (k < 64)
+  {
+    Log_DebugPrintf("Only %u of 64 coefficients in block, skipping", k);
+    return false;
+  }
+
+  IDCT(blk);
+  return true;
+}
+
+void MDEC::IDCT(s16* blk)
+{
+  std::array<s64, 64> temp_buffer;
+  for (u32 x = 0; x < 8; x++)
+  {
+    for (u32 y = 0; y < 8; y++)
+    {
+      s64 sum = 0;
+      for (u32 u = 0; u < 8; u++)
+        sum += s32(blk[u * 8 + x]) * s32(m_scale_table[u * 8 + y]);
+      temp_buffer[x + y * 8] = sum;
+    }
+  }
+  for (u32 x = 0; x < 8; x++)
+  {
+    for (u32 y = 0; y < 8; y++)
+    {
+      s64 sum = 0;
+      for (u32 u = 0; u < 8; u++)
+        sum += s64(temp_buffer[u + y * 8]) * s32(m_scale_table[u * 8 + x]);
+
+      blk[x + y * 8] = static_cast<s16>(std::clamp<s32>(SignExtendN<9, s32>((sum >> 32) + ((sum >> 31) & 1)), -128, 127));
+    }
+  }
+}
+
+void MDEC::yuv_to_rgb(u32 xx, u32 yy, const std::array<s16, 64>& Crblk, const std::array<s16, 64>& Cbblk,
+                      const std::array<s16, 64>& Yblk, std::array<u32, 256>& rgb_out)
+{
+  for (u32 y = 0; y < 8; y++)
+  {
+    for (u32 x = 0; x < 8; x++)
+    {
+      s16 R = Crblk[((x + xx) / 2) + ((y + yy) / 2) * 8];
+      s16 B = Cbblk[((x + xx) / 2) + ((y + yy) / 2) * 8];
+      s16 G = static_cast<s16>((-0.3437f * static_cast<float>(B)) + (-0.7143f * static_cast<float>(R)));
+
+      R = static_cast<s16>(1.402f * static_cast<float>(R));
+      B = static_cast<s16>(1.772f * static_cast<float>(B));
+
+      s16 Y = Yblk[x + y * 8];
+      R = static_cast<s16>(std::clamp(static_cast<int>(Y) + R, -128, 127));
+      G = static_cast<s16>(std::clamp(static_cast<int>(Y) + G, -128, 127));
+      B = static_cast<s16>(std::clamp(static_cast<int>(Y) + B, -128, 127));
+
+      R += 128;
+      G += 128;
+      B += 128;
+
+      rgb_out[(x + xx) + ((y + yy) * 16)] = ZeroExtend32(static_cast<u16>(R)) |
+                                            (ZeroExtend32(static_cast<u16>(G)) << 8) |
+                                            (ZeroExtend32(static_cast<u16>(B)) << 16);
+    }
+  }
+}
+
+void MDEC::y_to_mono(const std::array<s16, 64>& Yblk, std::array<u8, 64>& r_out)
+{
+  for (u32 i = 0; i < 64; i++)
+  {
+    s16 Y = Yblk[i];
+    Y = SignExtendN<10, s16>(Y);
+    Y = std::clamp<s16>(Y, -128, 127);
+    Y += 128;
+    r_out[i] = static_cast<u8>(Y);
+  }
+}
+
+void MDEC::HandleSetQuantTableCommand()
+{
+  // TODO: Remove extra copies..
+  std::array<u32, 16> packed_data;
+  m_data_in_fifo.PopRange(packed_data.data(), static_cast<u32>(packed_data.size()));
+  std::memcpy(m_iq_y.data(), packed_data.data(), m_iq_y.size());
+
+  if (!m_data_in_fifo.IsEmpty())
+  {
+    m_data_in_fifo.PopRange(packed_data.data(), static_cast<u32>(packed_data.size()));
+    std::memcpy(m_iq_uv.data(), packed_data.data(), m_iq_uv.size());
+  }
 }
 
-void MDEC::HandleCommand()
+void MDEC::HandleSetScaleCommand()
 {
-  Log_DebugPrintf("MDEC command: 0x%08X", m_data_in_fifo.Peek(0));
+  // TODO: Remove extra copies..
+  std::array<u32, 32> packed_data;
+  m_data_in_fifo.PopRange(packed_data.data(), static_cast<u32>(packed_data.size()));
+  std::memcpy(m_scale_table.data(), packed_data.data(), m_scale_table.size() * sizeof(s16));
 }
diff --git a/src/pse/mdec.h b/src/pse/mdec.h
index eac24c42e..77a5d8aa1 100644
--- a/src/pse/mdec.h
+++ b/src/pse/mdec.h
@@ -2,8 +2,7 @@
 #include "common/bitfield.h"
 #include "common/fifo_queue.h"
 #include "types.h"
-#include <string>
-#include <vector>
+#include <array>
 
 class StateWrapper;
 
@@ -28,8 +27,8 @@ public:
   void DMAWrite(u32 value);
 
 private:
-  static constexpr u32 DATA_IN_FIFO_SIZE = 256;
-  static constexpr u32 DATA_OUT_FIFO_SIZE = 256;
+  static constexpr u32 DATA_IN_FIFO_SIZE = 1048576;
+  static constexpr u32 DATA_OUT_FIFO_SIZE = 1048576;
 
   enum DataOutputDepth : u8
   {
@@ -39,6 +38,14 @@ private:
     DataOutputDepth_15Bit = 3
   };
 
+  enum class Command : u8
+  {
+    None = 0,
+    DecodeMacroblock = 1,
+    SetIqTab = 2,
+    SetScale = 3
+  };
+
   union StatusRegister
   {
     u32 bits;
@@ -63,19 +70,49 @@ private:
     BitField<u32, bool, 29, 1> enable_dma_out;
   };
 
+  union CommandWord
+  {
+    u32 bits;
+
+    BitField<u32, Command, 29, 3> command;
+    BitField<u32, DataOutputDepth, 27, 2> data_output_depth;
+    BitField<u32, bool, 26, 1> data_output_signed;
+    BitField<u32, u8, 25, 1> data_output_bit15;
+    BitField<u32, u16, 0, 16> parameter_word_count;
+  };
+
   void SoftReset();
   void UpdateStatusRegister();
 
-  void WriteCommandRegister(u32 value);
   u32 ReadDataRegister();
+  void WriteCommandRegister(u32 value);
+
+  void HandleDecodeMacroblockCommand();
+  void HandleSetQuantTableCommand();
+  void HandleSetScaleCommand();
+
+  const u16* DecodeColoredMacroblock(const u16* src, const u16* src_end);
+  const u16* DecodeMonoMacroblock(const u16* src, const u16* src_end);
+
+  // from nocash spec
+  bool rl_decode_block(s16* blk, const u16*& src, const u16* src_end, const u8* qt);
+  void IDCT(s16* blk);
+  void yuv_to_rgb(u32 xx, u32 yy, const std::array<s16, 64>& Crblk, const std::array<s16, 64>& Cbblk,
+                  const std::array<s16, 64>& Yblk, std::array<u32, 256>& rgb_out);
+  void y_to_mono(const std::array<s16, 64>& Yblk, std::array<u8, 64>& r_out);
 
-  void HandleCommand();
-  
   System* m_system = nullptr;
   DMA* m_dma = nullptr;
 
-  StatusRegister m_status_register = {};
-  
+  StatusRegister m_status = {};
+
   InlineFIFOQueue<u32, DATA_IN_FIFO_SIZE> m_data_in_fifo;
   InlineFIFOQueue<u32, DATA_OUT_FIFO_SIZE> m_data_out_fifo;
+  Command m_command = Command::None;
+  u32 m_command_parameter_count = 0;
+
+  std::array<u8, 64> m_iq_uv{};
+  std::array<u8, 64> m_iq_y{};
+
+  std::array<s16, 64> m_scale_table{};
 };